Tongass National Forest

Picket weirs raise concerns for fish movement especially for steelhead.  Because of potential negative impacts to stocks and the expense of picket weir operations, the Craig District entered into a pilot project to remotely detect fish movement via resistivity fish counting methods. These methods estimate steelhead escapement and compare daily upstream and downstream fish movement from the resistivity counter to actual fish catch at the picket weir.

Picket fence weir in stream

Resistive Weir

A resistivity counter detects the passage of fish across a series of three sensing elements (electrodes) affixed to a mat in the riverbed. It monitors the resistance of the water above the electrodes located on the stream bottom. A resistivity fish counting station was installed upstream of the Harris River picket weir in the spring 2005.

Actual counts and associated digital video data provided information on total steelhead numbers, size distribution and run timing. A final report is pending.

Resistive weir from a distance